Fastener driving tool

ABSTRACT

A pneumatically operated automatically cycling fastener driving tool includes a housing having a cavity defining a fluid reservoir. A cylinder is provided in the housing for slideably receiving a piston therein. A cylinder valve is provided for controlling the admission of fluid to and the exhaustion of fluid from one end of the cylinder. A suitable trigger arrangement is effective when depressed to exhaust the cylinder valve to atmosphere, and when released to connect the cylinder valve to the reservoir. An automatic cycling valve controls such admission to and discharge from the cylinder valve and is responsive to the pressure buildup in the upper end of the cylinder at the end of the driving stroke to switch the cylinder valve from exhaust to the reservoir to effect closing of the cylinder valve and the return stroke of the piston.

United States Patent Inventor Allen R. Obergfell Park Ridge, Ill.728,128

May 10, 1968 Feh. 9, 1971 Fastener Corporation Franklin Park, Ill.

a corporation of Illinois Appl. No. Filed Patented Assignee FASTENERDRIVING TOOL 20 Claims, 12 Drawing Figs.

U.S. Cl 91/252, 91/308, 91/309, 91/318, 91/399 Int. Cl F0ll 31/00, F01125/06 Field of Search 9l/(card), 220, 252, 308, 309

References Cited UNITED STATES PATENTS 2/1969 Bade 91/309 m: 43 llllrlly,2 A 44 vll/1111111137111111",l

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all" HIL l 3,278,103 |o/1966 Juilfsetal 3,278,104 i0/1966 Bement,...

` Primary Examiner-Paul E. Maslousky Attorney-Mason, Kolehmainen,Rathbum & Wyss ABSTRACT: A pneumatically operated automatically cycling'i fastener driving tool includes a housing having a cavity defining afluid reservoir. A cylinder is provided in the housing for slideablyreceiving a piston therein. A cylinder valve is provided for controllingthe admission of fluid to and the ex- "haustion of fluid from one end ofthe cylinder. A suitable .e trigger arrangement is effective whendepressed to exhaust the cylinder valve to atmosphere, and when releasedto connect the cylinder valve to the reservoir. An automatic cyclingvalve controls such admission to and discharge from the cylinder v valveand is responsive to the pressure buildup in the upper end of thecylinder at the end of the driving stroke to switch the cylinder valvefrom exhaust to the reservoir to effect closing of the cylinder valveand the return stroke of the piston.

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ATT'YS PATENIEU rfa man SHEET 8 0F 8 y NVEN'UR.' ALLEN R. OBERGFELLFASTENER DRIVING TOOL This invention relates to a fastener driving tooland, more particularly, to a fastener driving tool including new andimproved control means providing for successive or repetitive fastenerdriving operations upon a single depression of the tool trigger.

Commercially available pneumatic fastener driving tools in the past havefrequently provided for a single fastener driving stroke upon eachdepression of the tool trigger. In order to provide rapid operation ofthe tool, it has been proposed to cycle the tool through a drive andreturn stroke upon a single depression of the trigger. Moreoversituations have arisen where it is desirable to drive a plurality offasteners in successive fastener driving operations and suitable shortintervals upon a single depression of the tool trigger. It is frequentlydesirable that such autofire fastener driving tools be adaptable forsingle-stroke operation, or for operation in a repetitive manner upon asingle depression of the tool trigger. Commercially availableautomatically firing tools commonly require switching from high speedrepetitive operation to the singlefire mode before a single fastener canbe driven. Most desirably such control of the tool should preferably beaccomplished without manual selection of the mode of operation and witha minimum effort by the operator.

An object of the present invention therefore is to provide a new andimproved pneumatically actuated fastener driving tool of the type tocontinuously and repetitively operate through its working cycle so longas the trigger thereof is depressed.

Another object of the present invention is to provide a fastener drivingapparatus having new and improved control means.

Yet a further object of the present invention is the provision of thefastener driving tool of the type wherein the tool will repetitively andcontinuously operate through its working cycle so long as the triggermember is depressed, and wherein the rate of recycling of the tool mayreadily be varied.

Yet a further object of the present invention is the provision of afastener driving tool of the type which may be conveniently actuated asa single-stroke tool or operated to continuously and repetitivelyoperate through its working cycle so long as the trigger thereof isdepressed.

Yet a further object is to provide a new and improved single-cycle orsnap-acting fastener driving tool wherein the tool cycles through both adrive stroke and a return stroke upon depression of the trigger withoutthe delay of releasing the trigger.

Further objects and advantages of the present invention will becomeapparent as the following description proceeds and the features ofnovelty which characterize the invention will be pointed out withparticularity in the claims annexed to and forming a part of thisspecification.

In accordance with these and other objects there is provided a new andimproved automatically cycling fastener driving tool. A known type ofcommercially available fastener driving tool includes a housing having acavity defining a fluid reservoir and containing a cylinder in thehousing slideably receiving a piston therein. A cylinder valve isprovided for controlling the admission of fluid to and the exhaustion offluid from one end of the cylinder. A return fluid chamber in thehousing communicates with the cylinder and is effective to move thepiston to its return stroke. In accordance with the present inventioncontrol means are provided for automatically recycling the fastenerdriving tool in response to the pressure buildup above the piston at thecompletion of its driving stroke. Such fluid under pressure above thepiston is effective to shift a valve element in a cycling valve toprovide for the return stroke of the drive piston. Subsequent bleedingof lthis fluid from the cycling valve will be effective to reset thevalve and initiate a second drive stroke of the drive piston. In aApreferred embodiment of the invention, a timing chamber strokefollowing depression of the tool trigger, thus causing a delay in therecycling of the tool after the first drive stroke. Such delay permitsthe operator selectively to operate the tool as a single-stroke tool, orby maintaining the trigger depressed` the operator may readily use thetool for repetitive operation. Subsequent firing of the tool after theinitial stroke will be at a faster orset rate.

Advantageously the present recycling control structure may beincorporated into an existing commercial line of singlestroke tools bythe mere replacement of the prior cylinder cap with a cap containing theimproved cycling valve, and drilling of an additional passageway in thehousing. Thus the tools may be most economically produced with a minimuminventory of replacement parts.

Many other objects and advantages of the present invention will becomeapparent from considering the following detailed description inconjunction with the drawings in which:

FIG. l is a fragmentary cross-sectional view of a fastener driving toolincorporating the present invention and illustrating the drive piston inits static or at rest position;

FIG. 2 is a cross-sectional view of the fastener driving tool of FIG. 1,illustrating the control valve arrangement;

FIG. 3 is a fragmentary cross-sectional view of the fastener drivingtool of FIG. l, illustrated during its drive stroke;

FIG. 4 is a fragmentary cross-sectional view of the fastener drivingtool of FIG. 1, illustrated with the drive piston at the bottom of itsdrive stroke;

FIG. 5 is a cross-sectional plan view of the control mechanism,illustrated in the position of FIG. 4;

FIG. 6 is a fragmentary cross-sectional view of the fastener drivingtool of FIG. 1, illustrated with the piston in its return stroke;

FIG. 7 is a fragmentary cross-sectional plan view of the controlmechanism of the fastener driving tool, illustrated in the same positionas FIG. 6;

FIG. 8 is a fragmentary cross-sectional plan of a control mechanism fora fastener driving tool according to another embodiment of the presentinvention;

FIG. 9 is a fragmentary sectional view of a control valve assemblyforming another embodiment of the invention shown in a normal position;

FIG. 10 is a fragmentary sectional view of the valve assembly of FIG. 9shown in an operated position;

FIG. l1 is a fragmentary sectional view of a control valve assemblyforming another embodiment of the invention shown in a normal position;and

FIG. l2 is a fragmentary sectional view illustrating the valve assemblyof FIG. l1 in an operated position.

Referring now to the drawings, there is fragmentarily illustrated afastener driving tool generally as l0, which embodies a cycling valveassembly to provide for autore of the tool according to the presentinvention. The tool 10 may be of generally known construction and, asillustrated, is similar to that described in the copending applicationSer. No. 602,728, filed Dec. 19, 1966, by Richard l-l. Doyle andassigned to the same assignee as the present invention. The tool 10comprises a housing 12 including a generally vertically extending heador forward portion 12a and a rearwardly extending hollow handle portion12b defining a fluid reservoir 16. Pressurized fluid such as compressedair is supplied to the fluid reservoir of the tool l0 by a suitableflexible line. The drive system for the tool 10 includes a main or powercylinder 18 mounted within the head portion 12a having an open upper end18a that is adapted to be selectively connected to the reservoir 16. Theopen upper end of the cylinder 18 is in engagement with a diaphragm typemain or cylinder valve assembly 20, here shown of the poppet type, underthe control of a control or trigger valve assembly and a cycling valveassembly according to the present invention. A fastener driving assembly24 slideably mounted within the cylinder 18 includes a work or drivepiston 26 and has connected thereto a depending driver blade member 28.The fastener driving assembly 24 is normally biased to a position withthe piston 26 adjacent the cylinder valve assembly 20` as illustrated inFIG. l. An exhaust valve assembly indicated generally as 32 is providedfor controlling the selective connection of the upper end of thecylinder 18 to the atmosphere When the tool l is to be operated,compressed fluid from the reservoir 16 enters the upper open end 18a ofthe cylinder 18 and drives the fastener driving assembly 24 downwardlyto engage and set a fastener or nail supplied to a drive tract 36 in anosepiece and nosepiece structure 38. The flow of compressed fluid intothe upper end of the cylinder 18 is controlled by the cylinder valveassembly which includes a diaphragm 40, the periphery of which isclamped between a cap 42 and a cover plate 43 against the head portion12a of the housing l2 and which seats against the upper edge 18a of thecylinder 18. The diaphragm 40 is resiliently biased against the upperedge surface 18a by a spring 44 located between the cap 42 and thediaphragm 40. The cylinder side of the diaphragm 40 is continuously incommunication with the fluid reservoir 16 through a suitable passageway46 so that pressurized fluid continuously acts against the cylinder sideof the diaphragm 40 tending to displace the diaphragm 40 from the edge18a of the cylinder 18. However pressurized fluid is also introduced tothe opposite side of the diaphragm 40 while the fastener driving tool isin a static or at rest position. The pressure acting above the diaphragm40 is eective to maintain 'the diaphragm 40 in a closed position, asillustrated in FIG. l. However if the pressurized fluid above thediaphragm 40 is discharged, the pressurized fluid through the passageway46 is effective to unseat the diaphragm 40 from the edge 18a of thecylinder 18 to dump pressurized fluid into the top of the main cylinder18 and to drive the drive piston 26 through a drive stroke.

When the fastener driving tool is at rest, or when the drive piston isin its return stroke, the open upper end of the cylinder 18 is exhaustedto the atmosphere through the exhaust valve assembly 32. ln theillustrated embodiment the exhaust valve assembly 32 comprises a hollowvalve stem S0 which is secured to the diaphragm and which connects theupper end of the cylinder to the atmosphere through a plurality ofsuitable exhaust passages 52. However when the drive piston is operatedthrough a fire or drive stroke, it is necessary for the upper end of thecylinder 18 to be closed, and to this end there is provided a valve seatS4 disposed adjacent the end of the valve stem 50 remote from thecylinder 18 and adapted to be engaged by the valve stem 50 when thediaphragm 40 is raised at the initiation of a drive stroke, therebyclosing off the upper end ofthe cylinder 18 to the atmosphere.

To provide for the return drive of the fastener driving assembly 24,there is provided an air return chamber 60 communicating with the lowerend of the cylinder 18 through a plurality of ports 62. Moreover thedrive piston 26 is provided with suitable one way valve means 63. Tothis end the piston 26 is provided with spaced peripheral grooves 64 and66, the upper one of which serves as a sealing groove while the lowerone 66 functions as the one way valve means 63 to provide for the bypassof pressurized fluid to the air return chamber 60. An O-ring 68 providedin the upper one of the grooves 64 functions as a sealing membereffecting a pneumatic seal between the piston 26 and the inner wall ofthe cylinder 18. To bypass around the groove 64 and O-ring 68, there isprovided a plurality of` air passageways 70 extending from the lower one66 of the grooves and communicating with a central cavity 26a in thepiston 26. An O-ring 72 defining a valve element is positioned withinthe lower one 66 of the grooves. The O-ring 72 is expandable upon aselected pressure differential between the upper and lower ends of thecylinder to the piston 26 so as to unseat from the ports of the airpassageways 70 to provide for fluid to bypass through the piston 26around the O-ring 72 and to supply air to the return chamber 60.

It will be understood that in the operation of the basic tool the piston26 and associated driver blade member 28 are driven downwardly through adrive stroke by the connection of the upper end 18a of the cylinder 18with the reservoir 16.

Since there is no significant restraint to the piston during itsdownward movement, the pressure above the piston 26 will not build upsufficiently to unseat the O-ring 72 until the piston 26 approaches thebottom of its drive stroke. At this point the pressure above the piston26 will continue to build up until it approaches the pressure in thereservoir 16 and the O-ring 72, functioning as a valve element, will beunseated from the ports of the air passageways 70, thereby providing asource of pressurized fluid to the air return chamber 60 through the airpassageway 62. l

To cushion the drive stroke of the piston 26, and to seal the lower endof the housing 12a when the piston 26 is at its lowermost position,there is provided a resilient annular bumper 74 at the lower end of thecylinder 18 which is engageable by the piston 26 as it is at the end ofits drive stroke. Fluid such as compressed air from the lower end of thecylinder normally vents through a blade opening 76 in a washer 78 at thelower end of the bumper 74. However when the piston 26 engages thebumper 74 as illustrated in FIG. 4, pressurized fluid which passesaround the O-ring 72 cannot vent to atmosphere through the blade opening76. Upon exhaustion of the open upper end 18a of the cylinder 18 to theatmosphere, the pressurized fluid in the air return chamber 60 willreenter the lower end of the cylinder 18 through the ports 62 and willdrive the piston 26 back to its normal or at rest position. Leakage ofair around the blade opening 76 is not rapid enough to prevent thereturn of the piston 26.

The operation of the tool 10 is under the control of a trigger valveassembly 80 and a cycling valve assembly 82 incorporated into the cap42. Referring first to the trigger valve assembly, which is of a knowntype, there is provided a valve chamber 84 within the housing l2containing a valve element in the form of a valve ball 86 operable by avalve pin 88 upon depression or release of' the trigger 90. The triggervalve assembly 80 functions as a three way valve, so that when thetrigger 90 is released, the valve ball 86 seats against an O-ring 92defining a valve seat and closes off an exhaust passageway 94 extendingfrom the valve chamber 84 and defined between the valve pin 88 and avalve retainer 96. With the valve ball 86 in this normal position, areservoir passageway 98 is placed in communication with the valvechamber 84 and pressurized fluid from the reservoir 16 is supplied to atrigger passageway 100 which also opens into the valve chamber 84.

Depression of the trigger 90 however is e`ective to unseat the valveball 86 from the valve seat 92 and to seat the valve ball 86 against aconfronting edge 102 of the passageway 98 also defining a valve seat.Thus the trigger passageway 100 is closed from communication with thereservoir 16, and is simultaneously exhausted to the atmosphere throughthe valve chamber 84 and the exhaust passageway 94.

For controlling the automatic cycling of the tool l0, as bestillustrated in FIGS. 2, 5 and 7, there is provided the cycling valveassembly 82 within the cap 42 ofthe tool 10 which is effective, afterfiring of the tool, to initiate recycling thereof in response to thepressure buildup in the cylinder 18 above the piston 26. Specificallythe head 42 forms a valve body defining a valve cylinder 106 of thedifferential type, having a small diameter portion 106a and a largediameter portion l06b. The cylinder 106 is open at the large diameterend and the cylinder threadingly receives a needle valve assembly 108. Aspool type valve element 110 of the differential diameter type isshiftably positioned within the cylinder 106 for movement from a normalposition, as illustrated in FIG. 2, to an operated position, asillustrated in FIGS. 5 and 7. The valve element 110 is provided with asmall diameter part 110a and a large diameter part 11011. An annulargroove 112 defined in the small diameter part 110a intermediate thelength thereof defines a fluid passageway. A first port 116 opens withinthe fluid passageway 112 and communicates with the cylinder valveassembly 20 through a passageway l 16a. A second port 118 opens into thelarge diameter portion 106b of the valve cylinder 106 and communicateswith the closed end of the cylinder through a passageway l18a opening inthe top of the valve seat 54. A third port 120 opens into the smalldiameter portion106a of the valve cylinder 106 intermediate the strokeof the valve element 110 so as to communicate with the fluid passageway112 when the valve element 110 is in its operated position, asillustrated in FIGS. 5 and 7, but opens into the small end of the valvecylinder 106 when the valve element 110 is in its normal position asindicated in F IG. 2. The third port 120 communicates with the reservoirthrough a suitable passageway 1201i. A fourth port 122 opens into thefluid passageway 112 when the valve element is in a normal position, asillustrated in FIG. 2, to a position blocked by the valve element 110when the valve element 110 is in an operated position, as illustrated inFIGS. 5 and 7. The fourth port 122 communicates with the trigger valveassembly 80 through the passageway 110.

ln operation the valve element l l is held in its normal positionillustrated in FIG. 2 by the fluid pressure from the reservoir 16 actingthrough the port 120. The valve element 1 10 is moved to its operatedposition, as illustrated in FIGS. and 7, by the buildup of fluidpressure within the cylinder 18 acting through the port l 18 and againstthe large diameter end of the valve element 110. The valve element 110will shift from its normal position to its operated position when thepressure acting on the large end thereof is sufficiently great toovercome the return bias of the reservoir pressure acting on the smallerend thereof. Moreover the valve element 110 will return to its normalposition and recycle the tool as soon as the fluid pressure acting onthe large diameter end 110b of the valve element l l0 is bled offsufficiently to permit return of the valve.

To adjustably control the rate of recycling of the tool, there isprovided the needle valve assembly 108 which restricts the exhaust ofthe fluid from the open end of the large diameter portion 106b of thevalve cylinder 106. As therein illustrated, the needle valve assembly108 includes a needle valve body 126 in the form of a sleeve threadedinto the large diameter portion 106b of the valve cylinder 106. Theneedle valve body has a generally inwardly tapered point 127 againstwhich an O-ring 128 can seat to define a check valve which will unseatto permit fluid flow from the port 118 toward the large diameter portion110b of' the valve element 110 and around ports 130 in a retaining ring132, as illustrated in FIG. 5. However the check valve element 128 willseat between the valve seat 127 and the inner wall of the valve cylinder106 to prevent reverse flow of the fluid, as illustrated in FIG. 7. Theneedle valve body 126 is provided with a longitudinal opening 134adjustably receiving a needle element 136 serving to throttle or meterthe escape flow of fluid from the large diameter portion 106b of thevalve cylinder. The rate of bleeding air from the large diameter portion106b will, of course, determine the recycling time of the tool.

To provide for single firing of the tool without having to manually setor adjust the tool, a time delay is provided between the f'irst andsecond driving strokes after initial actuation of the trigger. The timedelay is accomplished through a timing chamber 140 communicating withthe valve cylinder 106 through a port 142 opening into the largediameter portion of the valve cylinder 106b and a passageway 142. Thetiming chamber 140 is effective to cause a delay in the pressure buildupafter the first stroke, but is not effective on succeeding strokes inthe same burst or depression of the trigger. Thus the tool has a veryimportant advantage of being easily used as a single shot tool or anautofire tool with no adjustment necessary by the operator. l

From the above detailed description of the improved fastener drivingtool, its operation is believed to be clear. However, briefly, it willbe understood that the drive piston 26 is actuated through a drivestroke by the unseating of the diaphragm 40 from the upper end 18a ofthe cylinder, and is returned through a return stroke upon reseating ofthe diaphragm 40 and opening of the exhaust valve assembly 32 toatmosphere through the exhaust passageway 52. The position of thediaphragm 40 is controlled by the provision of pressurized fluid abovethe diaphragm, or the exhaustion thereof y the arrows A in FIG. 2, Atthe same time the valve element is held in its at rest position by thepressure of the fluid from the reservoir acting through the passagewayl20a and port against the small diameter end of the valve element 110,as illustrated by the arrows B in FIG. 2. The remaining ports of thecycling control valve assembly 80 are at atmospheric pressure.

Upon depression of the trigger, the cylinder valve 20 is exhausted toatmosphere through the passageway 116a, ports 116 and 122, around thefluid passageway 112, through the passageway 110, and into the triggervalve chamber 84 and the exhaust passageway 94. With the exhaustion offluid from above the diaphragm 40, the cylinder valve 20 will snap open,dumping pressurized fluid above the piston 26 and driving the piston 26through a drive stroke, as illustrated in FIG. 3. The pressure buildupabove the cylinder during the drive stroke of the piston 26 is notsufficiently great to affect the position of the valve element 110.However as soon as the piston 26 reaches the end of' its drive stroke,as illustrated in FIG. 4, pressure will begin to build up in thecylinder 18 above the piston 26. This buildup of pressure will result inan unseating of the O-ring 72 to permit fluid to pass through the oneway valve means 63 into the air return chamber 60. At the same time thebuildup of pressure will be effective to act through the opening in thehollow valve stem 50 and through the passageway 1l8a and port 1 18, tounseat the check valve 128 and act against the large diameter part 1l0bof the valve element 110. As soon as the pressure acting against thelarge diameter part 1 l0 is sufficient to overcome the return force ofthe reservoir pressure acting against the small diameter portion 11011of the valve element 110 the valve element 110 will shift to theposition illustrated in FIG. 5. However due to the volume of air whichmust enter the reserve chamber 140, there will be a short time delay inthe buildup of pressure and accordingly the valve element 110 will notshift immediately. The size of the chamber l 10 and connectingpassageway 142a will, of course, determine the time delay. The flow ofthis signal fluid from the cylinder 18 will follow along the path of thearrows indicated as C, FIG. 5.

Upon shifting of the valve element 110 to its operated position, asillustrated in FIG. 7, fluid will now be directed from the reservoir 16through the passageway 120a, ports 120 and 116, around the fluidpassageway 112, and through the passageway 116a to the top of thecylinder valve 20 as illustrated by arrows D, FIG. 7, whereupon thecylinder valve 20 will close by having the diaphragm 40 thereof seatagainst the upper edge 18a of the cylinder 18. The closing of thecylinder valve 20 will be effective to unseat the hollow valve stem 50from the valve seat 54 and to exhaust the upper end of the cylinder 18to atmosphere through the exhaust passageway 52. Fluid will bleed fromthe timing chamber around the needle valve 136, as indicated by thearrows E, FIG. 7. The check valve 128 will, of course, seat between thetapered portion 127 and the inner wall of the valve cylinder 106b toprevent return flow of the fluid from the timing chamber 140 to theupper end of the piston 18. As soon as the pressure acting on the largediameter part 110b drops sufficiently to permit reshifting of the valveelement 110 to its normal position, the valve element 110 will shift,exhausting the cylinder valve 20 and recycling the tool. Such recyclingwill continue so long as the trigger 90 remains depressed.

Since only a portion of the pressure from the timing chamber 140 has hadtime to bleed out, repetitive cycling of the tool will occur morerapidly than took place following the metering is illustrated in FIG 8.Similar components in the embodiments of FIG. 8 and FIGS 1 through 7 areidentified by the same reference numerals. As therein shown, there isprovided a cycling valve assembly 148, similar to the cycling assembly82 heretofore described. but having a sealing O-ring 150 that replacesthe check valve 128. The cycling valve assembly 148 is further providedwith a port 152 which extends through the side of the needle valve body126 so as to place the signal air from the port 118 into communicationwith the longitudinal opening of the needle valve. Thus the signal airduring the buildup of pressure in the timing reservoir 140 must bemetered past a needle valve 154. If` desired, the needle valve 154 couldbe identical with the needle valve 136 previously described. Similarlythe fluid from the reservoir 140 must be metered past the needle valve154 during its discharge to atmosphere. Such discharge to atmospherewill now take place through the port 118, the chamber 134, the port 152,the signal passageway 118, and through the exhaust passageway 52.

FIGS. 9 and l0 illustrate an embodiment of the invention which providesvery accurate recycling of the tool by utilizing a bleed from thereservoir to return the cycle valve. Similar components of theembodiment of FIGS. 9 and 10 and of the prior embodiments are identifiedby the same reference numerals. As therein shown, there is provided acycling valve assembly 160, similar to the cycling assembly 82heretofore described, but using sealing O-rings on the spool valverather than metal to metal engagement with subsequent seepage for thereturn force. More specifically, the` cycling valve assembly 160includes a valve cylinder 162 open at both ends having a spool typevalve element 164 sldeably received therein, as well as the needle valveassembly including the needle valve body 126 and the needle valve 154.As heretofore described, the port 152 extends through the side of theneedle valve body 126 so as to place the signal air from the port 1 18into communicaton with the longitudinal opening of the needle valve.Thus the signal air during the buildup of pressure in the timingreservoir 140 must be metered past the needle valve 154 in the mannerheretofore described. Similarly the fluid from the air reservoir 140must be metered past the needle valve 154 during its discharge to theatmosphere.

Referring now to the spool type valve element 164 in accordance with thepresent embodiment, the spool valve element 164 is of the differentialdiameter type, having a plurality of spaced O-rings 168, 170 and 172,each defining piston means on the valve element 164 sldeably receivedwithin a large diameter portion 162a of the valve cylinder 162, andadditionally includes an additional O-ring 174 also defining pistonmeans on the valve element 164 and sldeably received within a reduceddiameter portion 162b of the valve cylinder 162. Intermediate theO-rings, the valve element 164 is of slightly reduced diameter toprovide annular passageways 178, 180 and 182. Moreover a bleedpassageway 184 is provided around the O-ring 172 and, along with theO-ring 172, acts as a check valve so that when the pressure buildup onthe left of the O-ring 172, as viewed in FIGS. 9 and 10, is greater thanthe pressure to the right thereof, fluid will be bled through the bleedpassageway 184, around the O-ring 172; however, when the pressure to theright of the O-ring 172 is greater, the O-ring 172 will be drivenagainst a shoulder 186 in an elongated O-ring groove 188 to block thereturn flow of fluid around the O-ring 172.

From the above description of the embodiment of FIGS. 9 and 10, theoperation of the improved control valve is believed clear. I-Iowever,briefly, it will be understood that with the absence of` signal ainfromthe port 118, the valve element 164 is biased to the left by thereservoir pressure entering port 120 and acting on the effectivedifferential diameters between the piston means defined by the O-rings172 and 174. The main or cylinder valve is connected to the reservoirpressure through the trigger control valve. When the trigger isdepressed the control valve is now opened to the atmosphere, thusventing the cylinder valve through the passageway 116,

180, and 122. The cylinder valve will now open, allowing the reservoirpressure to drive the drive piston downwardly to complete the workstroke. Pressure builds up in the main cylinder of the tool and exhaustpassageways thus creating a signal pressure to the cycling valveassembly entering through the passageway 118. After filling the delaychamber 140 of the cycling valve assembly, the signal fluid is effectiveto bias the valve element 164 to the right, to the position illustratedin FIG. 10. Thisshift is rapid since the only return bias is the trappedfluid between the O-rings 172 and 174 acting on the effective diameterdifferences of the O-rings. Shifting of the valve element 164 to theright connects the reservoir directly to the cylinder valve through thepassageways 120, and 116. The O-ring 170 has moved between the ports 116and 122 to block the communication of the trigger from the reservoir. Asthe work cylinder pressure and the signal pressure are dissipated to theatmosphere, the trapped air between the O-rings 172 and 174 shift thevalve element 164 to the left, starting the recycling of the tool,providing of course that the trigger has not yet been released. Theshifting of the cycle valve to the left is now slow enough to allowfulllne pressure to build up above the cylinder valve, insuring positiveclosure. This minimizes any unstable or erratic operation of thecylinder valve.

A tool according to the present invention may readily be converted forsingle-cycle operation. Such an embodiment is illustrated in FIGS. 11and 12. Similar components in the embodiment of FIGS. 11 and and theprevious embodiments are identified by the samelreference numerals.Referring now specifically to FIGS. 11 and 12, there is provided asinglecycle control valve assembly including a valve cylinder 192containing both a spool-type valve element 194 and a needle valve body126, similar to that heretofore described, but provided with an end plug196 rather than the conventional needle valve. The valve cylinder 192 isof the differential diameter type, having an enlarged portion 192a and areduced diameter portion 192b. The port 152 is provided through the sideof the needle valve body 126 so as to place signal air from the signalairport 118 intocommunication with the longitudinal opening 198 of theneedle valve body.

Referring now to the construction of the valve element 194, the valveelement is of the differential diameter type, sldeably received withinthe valve cylinder 192. A first O-ring 200 defining piston means iscontained on the valve element 194 sldeably received within the largediameter portion 192a of the valve cylinder 192. Additional spacedO-rings 202, 204 and 206 are received on the spool-type valve element194 sldeably received within the reduced diameter portion l92b of thevalve cylinder 192. The valve element 194 is formed with reduceddiameter portions between the O-rings 200, 202, 204 and 206 so as todefine annular passageways 210, 212 and 214.

From the above brief description, the operation of the single-cycleaction valve is believed clear. ln the static position illustrated inFIG. ll, the valve element 194 is positioned to the left with thecylinder valve of the tool being connected through the trigger to thereservoir, including the passageways 116, 212 and 122 of the controlvalve assembly 190. Direct reservoir pressure through the control valveassembly 190 is blocked by the O-rings 204 and 206. Moreover signalpressure through the signal passageway 118 is absent, as the exhaust ofthe tool is opened to the atmosphere.

When the trigger is depressed, shutting off the reservoir air to thecylinder valve, and allowing this pressure to vent to the atmosphere,the cylinder valve will open exposing the work piston to the fullreservoir pressure. The work piston will then move downwardly throughthe drive stroke, and the cylinder exhaust valve will be closed causinga buildup of pressure in the main cylinder. Pressurized fluid from themain cylinder will pass through the signal passageway 118 to act on theeffective diameter defined by the O-ring 200. As soon as sufficientforce has built up on the O-ring diameter 200, the valve element 194will shift to the right, to the position illustrated in FlG. l2, inwhich position the element 194 connects the cylinder valve with thedirect reservoir pressure through the passageways 120, 212 and 116 ofthe control valve assembly 119. The cylinder valve will close, whichoperation opens the exhaust valve, dissipates the signal, and allows thedrive piston to return t the normal position. While the trigger isdepressed, the trigger passage 122 is blocked by the O-rings 200 and202. However assoon as the trigger is released, the reservoir pressurewill be provided through the trigger and through the trigger passageway122 to act on the differential diameter portions of the valve element194 defined by the difference in the diameter of O-rings 200 and 202.The tool is now ready'to go through another single-cycle stroke as soonas the trigger is again depressed.

lclaim:

1. A pneumatically operated fastener driving tool including a housinghaving a cavity defining a fluid reservoir; a cylinder in said housing;a piston slideably mounted in the cylinder; cylinder valve meanscontrolling admission of fluid to and the exhaustion of fluid from oneend of the cylinder; cycling means for automatically cycling said pistonto provide for multiple firing of said tool, said cycling means beingconnected with said reservoir, said one end of said cylinder, and saidcylinder valve means; trigger valve means movable between an operatedand an unoperated position to connect said cycling means selectively toexhaust and to said reservoir; and means establishing a delay only priorto the initiation of the second cycle of operation during each continuedoperation of said trigger valve.

2. A pneumatically operated fastener driving tool including a housinghaving a cavity defining a fluid reservoir; a cylinder in said housing;a piston slideably mounted in the cylinder; cylinder valve meanscontrolling admission of fluid to and the exhaustion of fluid from oneend of the cylinder; a`control passage; a trigger valve means foralternately connecting the control passage to the reservoir and theatmosphere; cycling means for automatically cycling said piston toprovide for multiple firing of said tool, said cycling means beingdirectly connected with said reservoir and being connected to saidcylinderv and said cylinder valve means, said cycling means including aspool valve with a first fluid surface connected to the fluid suppliedto the cycling means by the reservoir to continuously bias the spoolvalve toward a first position placing said cylinder valve means incommunication with said control passage, said spool valve having asecond fluid surface supplied with the pressure in said cylinder to movethe spool valve to a second position connecting the fluid continuouslysupplied to the cycling means from said reservoir to said cylinder valvemeans.

3. A fastener driving tool as set forth in claim 2 including a timingchamber, and meteringmeans connecting said timing chamber to saidcylinder to retard the pressure buildup acting on said spool valve uponinitial cycling after operation of said trigger valve means.

4. A pneumatically operated fastener driving tool including a housinghaving a cavity defining a fluid reservoir; a cylinder in said housing;a piston slideably mounted in the cylinder; cylinder valve meanscontrolling admission of fluid to and the exhaustion of fluid from oneend of said cylinder in response to the exhaustion of fluid from saidcylinder valve and the admission of fluid from said reservoir to saidcylinder valve; a cycling control valve; first passage means connectingsaid cycling control valve to said cylinder valve means; second passagemeans connecting said cycling valve to said cylinder; third passagemeans continuously connecting said cycling valve to said reservoir;fourth passage means connected to said cycling valve; and a triggervalve connected to said cycling control valve through said fourthpassage means effective Vwhen depressed to exhaust said cycling controlvalve and when released to connect said cycling control valve to thereservoir; said cycling valve including a spool valve element of thedifferential type having a small diameter end and a large diameter end,said reservoir communicating with said small diameter end through saidthird passage means to continuously bias the spool valve toward a normalposition connecting said first and fourth passage means, said cylindercommunicating with said large diameter end through said second passagemeans and responsive to a fluid pressure buildup in the cylinder toshift the spool valve to an operated position connecting said first andthird passage means.

5. A fastener driving tool as set forth in claim 4 including a timingchamber communicating with said second passage means to provide a delayin the first recycling stroke of said tool.

6. A fastener driving tool as set forth in claim 5 including exhaustmeans exhausting the large diameter end of said spool valve and saidtiming chamber to atmosphere.

7. A fastener driving tool as set forth in claim 6 including throttlingmeans throttling said exhaust valve.

8. A fastener driving tool as set forth in claim 7 wherein saidthrottling means includes an adjustable needle valve for regulating therate of recycling of said tool.

9. A fastener driving tool as set forth in claim 5 including check valvemeans in said second passage means intermediate said timing chamber andsaid one end of said cylinder preventing return flow from said timingchamber to said one end of said cylinder.

10. A pneumatically operated fastener driving tool including a housinghaving a cavity defining a fluid reservoir; a cylinder in said housing;a piston slideably mounted in the cylinder; cylinder valve meanscontrolling admission of fluid to and the exhaustion of fluid from oneend of the cylinder in response to the exhaustion of fluid from saidcylinder valve and the admission of fluid from said reservoir to saidcylinder valve, a cycling control valve including a valve body in saidhousing defining a valve cylinder of the differential type having asmall diameter portion and a large diameter portion, said valve cylinderopen at the large diameter end, a spool-type valve element of thedifferential diameter type shiftably positioned in said valve cylinderfor movement between a normal and an operated position and having asmall diameter part and a large diameter part, structure on said smalldiameter part defining a fluid passageway, first passage means openingin said fluid passageway and communicating with said cylinder valvemeans when said valve element is in both of the normal and operatedpositions; second passage means opening into said large diameter portionand communicating with said cylinder, third passage means opening intosaid small diameter portion of said valve cylinder intermediate thestroke of said valve element so as to communicate with said fluidpassageway only when said valve element is in said operated position andcommunicating with said reservoir, fourth passage means opening intosaid fluid passageway only when said valve element is in a normalposition; a trigger valve connected to said cycling control valvethrough said fourth passage means effective when depressed to exhaustsaid cycling control valve and when released to connect said cyclingcontrol valve to the reservoir; throttling means including an adjustableneedle valve for restricting the exhaust of fluid from the open end ofsaid large diameter portion; and check valve means in said secondpassage means permitting fluid flow only out of said`one end of saidcylinder.

11. A fastener driving tool as set forth in claim 10 including a timingchamber communicating with said large diameter portion of said valvecylinder.

l2. A fastener driving tool including a housing having cylinder means;cycling means slideably mounted in the cylinder means; cycling means forautomatically cycling said piston means to provide for multiple firingof said tool; control means operatively associated with said cyclingmeans to initiate cycling thereof; and delay means operativelyassociated with said cycling means for providing a delay in the refiringof said tool between the first and second operations of said pistonmeans after initiation of the cycling thereof.

13. A fastener driving tool as set forth in claim 12 wherein saidhousing includes a cavity defining a fluid reservoir, and

said cylinder means is operatively connected to said reservoir throughsaid cycling means to provide for pneumatic firing of said tool.

14. A fastener driving tool as set forth in claim l2 wherein saidcontrol means is a manually operable trigger valve operable between anoperated and an unoperated position for initiating cycling of said toolwhereby said delay is provided after the first cycle of operation ofsaid tool following movement of said trigger valve to an operatedposition.

l5. A fastener driving tool including fastener driving means, controlmeans for initiating automatic repetitive cycling of said fastenerdriving means, and delay means effective during continued operation ofthe control means for providing a delay in the recycling of saidfastener driving means to cause the first cycle of the fastener drivingmeans to take longer than the second and following cycles of thefastener driving means.

16. A pneumatically operated fastener driving tool including a housinghaving a cavity defining a fluid reservoir; a cylinder in said housing;a piston slideably mounted in the cylinder; cylinder valve meanscontrolling admission of fluid to and the exhaustion of fluid from oneend of the cylinder; cycling means for automatically cycling said pistonthrough a drive and return stroke, said cycling means including a valvehaving a first fluid responsive surface supplied with fluid directlyfrom said reservoir and continuously biased thereby to a normal positionand a second fluid responsive surface continuously coupled to saidcylinder and biased by pressure admitted to the cylinder to an operatedposition, an inlet passage, and an outlet passage continuously coupledto said cylinder valve means; and trigger valve means movable between anoperated and an unoperated position and connected in said inlet passageto connect said cycling means selectively to exhaust and to saidreservoir.

17. A pneumatically operated fastener driving tool including a housinghaving a cavity defining a fluid reservoir; a cylinder in said housing;a piston slideably mounted in the cylinder; cylinder valve meanscontrolling admission of fluid to and the exhaustion of fluid from oneend of said cylinderin response to the exhaustion of fluid from saidcylinder valve and the admission of fluid from said reservoir to saidcylinder valve, a cycling control valve including a valve body in saidhousing defining a valve cylinder of the differential type having asmall diameter portion and a large diameter portion, said cylinder openat both ends, a spool-type element of the differential diameter typeshiftably positioned in said cylinder for movement between a normal andan operated position having a small diameter part and a large diameterpart, means defining first, second and third piston means on said valveelement slideably received in said large diameter portion, and fourthpiston means defining a seal slideably received in said small diameterportion, means on said large diameter part intermediate said first andsecond piston means defining a first fluid passageway, means on saidlarge diameter part intermediate said second and third piston meansdefining a second fluid passageway; first passage means opening in saidsecond fluid passageway and communicating with said cylinder valvemeans; second passage means opening into said valve cylinder andcommunicating with said one end of said cylinder, third passage meansopening into said large diameter portion of said valve cylinderintermediate the stroke of said third piston means so as to communicatewith said second fluid passageway when said valve element is in saidoperated position and communicating with said reservoir, fourth passagemeans opening into said second-fluid passageway when said valve elementis in a normal position and intermediate the stroke of said secondpiston means; a trigger valve connected to said cycling control valvethrough said fourth passage means effective when depressed to exhaustsaid cycling control valve and when released to connect said cyclingcontrol control valve to the reservoir; and throttling means restrictingthe exhaust of fluid from the open end of said large diameter portion. l

18. A fastener driving tool as set forth in claim 17 including checkvalve bleeding means around said third piston means providing for fluidflow into the differential portion of said cylinder for return of saidvalve element to a normal position,

19. A fastener driving tool as set forth in claim 17 including a delaychamber communicating with said large diameter portion of said valvecylinder beyond the stroke of said first piston means.

20. A pneumatically operated fastener driving tool including a housinghaving a cavity defining a fluid reservoir; a cylinder in said housing;a piston slideably mounted in the cylinder; cylinder valve meanscontrolling admission of fluid to and the exhaustion of fluid from oneend of said cylinder in response to the exhaustion of fluid from saidcylinder valve and the admission of fluid from said reservoir to saidcylinder valve, a control valve including a valve body in said housingdening a valve cylinder of the differential type having a small diameterportion and a large diameter portion, said cylinder open at both ends, aspool-type valve element of the differential diameter type shiftablypositioned in said cylinder for movement between a normal and anoperated position having a small diameter part and a largeA diameterpart, means defining first piston means on said valve element slideablyreceived in said large diameter portion, and means defining second,third and fourth piston means on said valve element slideably receivedin said small diameter portion, first fluid passageway defined betweensaid first and second piston means, second fluid passageway definedbetween said second and third piston means, and third fluid passagewaydefined between said third and fourth piston means; first passage meansopening in said second fluid passage means and communicating with saidcylinder valve means; second passage means opening into said valvecylinder and communicating with said one end of said cylinder, thirdpassage means opening into said small diameter portion of said valvecylinder intermediate the stroke of said third piston and communicatingwith said reservoir, fourth passage means opening into said valvecylinder intermediate the stroke of said fourth piston means; and atrigger valve connected to said control valve through said fourthpassage means effective when depressed to exhaust said control valve andwhen released to connect said control valve to the reservoir.

1. A pneumatically operated fastener driving tool including a housinghaving a cavity defining a fluid reservoir; a cylinder in said housing;a piston slideably mounted in the cylinder; cylinder valve meanscontrolling admission of fluid to and the exhaustion of fluid from oneend of the cylinder; cycling means for automatically cycling said pistonto provide for multiple firing of said tool, said cycling means beingconnected with said reservoir, said one end of said cylinder, and saidcylinder valve means; trigger valve means movable between an operatedand an unoperated position to connect said cycling means selectively toexhaust and to said reservoir; and means establishing a delay only priorto the initiation of the second cycle of operation during each continuedoperation of said trigger valve.
 2. A pneumatically operated fastenerdriving tool including a housing having a cavity defining a fluidreservoir; a cylinder in said housing; a piston slideably mounted in thecylinder; cylinder valve means controlling admission of fluid to and theexhaustion of fluid from one end of the cylinder; a control passage; atrigger valve means for alternately connecting the control passage tothe reservoir and the atmosphere; cycling means for automaticallycycling said piston to provide for multiple firing of said tool, saidcycling means being directly connected with said reservoir and beingconnected to said cylinder and said cylinder valve means, said cyclingmeans including a spool valve with a first fluid surface connected tothe fluid supplied to the cycling means by the reservoir to continuouslybias the spool valve toward a first position placing said cylinder valvemeans in communication with said control passage, said spool valvehaving a second fluid surface supplied with the pressure in saidcylinder to move the spool valve to a second position connecting thefluid continuously supplied to the cycling means from said reservoir tosaid cylinder valve means.
 3. A fastener driving tool as set forth inclaim 2 including a timing chamber, and metering means connecting saidtiming chamber to said cylinder to retard the pressure buildup acting onsaid spool valve upon initial cycling after operation of said triggervalve means.
 4. A pneumatically operated fastener driving tool includinga housing having a cavity defining a fluid reservoir; a cylinder in saidhousing; a piston slideably mounted in the cylinder; cylinder valvemeans controlling admission of fluid to and the exhaustion of fluid fromone end of said cylinder in response to the exhaustion of fluid fromsaid cylinder valve and the admission of fluid from said reservoir tosaid cylinder valve; a cycling control valve; first passage meansconnecting said cycling control valve to said cylinder valve means;second passage means connecting said cycling valve to said cylinder;third passage means continuously connecting said cycling valve to saidreservoir; fourth passage means connected to said cycling valve; and atrigger valve connected to saiD cycling control valve through saidfourth passage means effective when depressed to exhaust said cyclingcontrol valve and when released to connect said cycling control valve tothe reservoir; said cycling valve including a spool valve element of thedifferential type having a small diameter end and a large diameter end,said reservoir communicating with said small diameter end through saidthird passage means to continuously bias the spool valve toward a normalposition connecting said first and fourth passage means, said cylindercommunicating with said large diameter end through said second passagemeans and responsive to a fluid pressure buildup in the cylinder toshift the spool valve to an operated position connecting said first andthird passage means.
 5. A fastener driving tool as set forth in claim 4including a timing chamber communicating with said second passage meansto provide a delay in the first recycling stroke of said tool.
 6. Afastener driving tool as set forth in claim 5 including exhaust meansexhausting the large diameter end of said spool valve and said timingchamber to atmosphere.
 7. A fastener driving tool as set forth in claim6 including throttling means throttling said exhaust valve.
 8. Afastener driving tool as set forth in claim 7 wherein said throttlingmeans includes an adjustable needle valve for regulating the rate ofrecycling of said tool.
 9. A fastener driving tool as set forth in claim5 including check valve means in said second passage means intermediatesaid timing chamber and said one end of said cylinder preventing returnflow from said timing chamber to said one end of said cylinder.
 10. Apneumatically operated fastener driving tool including a housing havinga cavity defining a fluid reservoir; a cylinder in said housing; apiston slideably mounted in the cylinder; cylinder valve meanscontrolling admission of fluid to and the exhaustion of fluid from oneend of the cylinder in response to the exhaustion of fluid from saidcylinder valve and the admission of fluid from said reservoir to saidcylinder valve, a cycling control valve including a valve body in saidhousing defining a valve cylinder of the differential type having asmall diameter portion and a large diameter portion, said valve cylinderopen at the large diameter end, a spool-type valve element of thedifferential diameter type shiftably positioned in said valve cylinderfor movement between a normal and an operated position and having asmall diameter part and a large diameter part, structure on said smalldiameter part defining a fluid passageway, first passage means openingin said fluid passageway and communicating with said cylinder valvemeans when said valve element is in both of the normal and operatedpositions; second passage means opening into said large diameter portionand communicating with said cylinder, third passage means opening intosaid small diameter portion of said valve cylinder intermediate thestroke of said valve element so as to communicate with said fluidpassageway only when said valve element is in said operated position andcommunicating with said reservoir, fourth passage means opening intosaid fluid passageway only when said valve element is in a normalposition; a trigger valve connected to said cycling control valvethrough said fourth passage means effective when depressed to exhaustsaid cycling control valve and when released to connect said cyclingcontrol valve to the reservoir; throttling means including an adjustableneedle valve for restricting the exhaust of fluid from the open end ofsaid large diameter portion; and check valve means in said secondpassage means permitting fluid flow only out of said one end of saidcylinder.
 11. A fastener driving tool as set forth in claim 10 includinga timing chamber communicating with said large diameter portion of saidvalve cylinder.
 12. A fastener driving tool including a housing havingcylinder means; cycling means slideably mounted in the cylinder meAns;cycling means for automatically cycling said piston means to provide formultiple firing of said tool; control means operatively associated withsaid cycling means to initiate cycling thereof; and delay meansoperatively associated with said cycling means for providing a delay inthe refiring of said tool between the first and second operations ofsaid piston means after initiation of the cycling thereof.
 13. Afastener driving tool as set forth in claim 12 wherein said housingincludes a cavity defining a fluid reservoir, and said cylinder means isoperatively connected to said reservoir through said cycling means toprovide for pneumatic firing of said tool.
 14. A fastener driving toolas set forth in claim 12 wherein said control means is a manuallyoperable trigger valve operable between an operated and an unoperatedposition for initiating cycling of said tool whereby said delay isprovided after the first cycle of operation of said tool followingmovement of said trigger valve to an operated position.
 15. A fastenerdriving tool including fastener driving means, control means forinitiating automatic repetitive cycling of said fastener driving means,and delay means effective during continued operation of the controlmeans for providing a delay in the recycling of said fastener drivingmeans to cause the first cycle of the fastener driving means to takelonger than the second and following cycles of the fastener drivingmeans.
 16. A pneumatically operated fastener driving tool including ahousing having a cavity defining a fluid reservoir; a cylinder in saidhousing; a piston slideably mounted in the cylinder; cylinder valvemeans controlling admission of fluid to and the exhaustion of fluid fromone end of the cylinder; cycling means for automatically cycling saidpiston through a drive and return stroke, said cycling means including avalve having a first fluid responsive surface supplied with fluiddirectly from said reservoir and continuously biased thereby to a normalposition and a second fluid responsive surface continuously coupled tosaid cylinder and biased by pressure admitted to the cylinder to anoperated position, an inlet passage, and an outlet passage continuouslycoupled to said cylinder valve means; and trigger valve means movablebetween an operated and an unoperated position and connected in saidinlet passage to connect said cycling means selectively to exhaust andto said reservoir.
 17. A pneumatically operated fastener driving toolincluding a housing having a cavity defining a fluid reservoir; acylinder in said housing; a piston slideably mounted in the cylinder;cylinder valve means controlling admission of fluid to and theexhaustion of fluid from one end of said cylinder in response to theexhaustion of fluid from said cylinder valve and the admission of fluidfrom said reservoir to said cylinder valve, a cycling control valveincluding a valve body in said housing defining a valve cylinder of thedifferential type having a small diameter portion and a large diameterportion, said cylinder open at both ends, a spool-type element of thedifferential diameter type shiftably positioned in said cylinder formovement between a normal and an operated position having a smalldiameter part and a large diameter part, means defining first, secondand third piston means on said valve element slideably received in saidlarge diameter portion, and fourth piston means defining a sealslideably received in said small diameter portion, means on said largediameter part intermediate said first and second piston means defining afirst fluid passageway, means on said large diameter part intermediatesaid second and third piston means defining a second fluid passageway;first passage means opening in said second fluid passageway andcommunicating with said cylinder valve means; second passage meansopening into said valve cylinder and communicating with said one end ofsaid cylinder, third passage means opening into said large diameteRportion of said valve cylinder intermediate the stroke of said thirdpiston means so as to communicate with said second fluid passageway whensaid valve element is in said operated position and communicating withsaid reservoir, fourth passage means opening into said second fluidpassageway when said valve element is in a normal position andintermediate the stroke of said second piston means; a trigger valveconnected to said cycling control valve through said fourth passagemeans effective when depressed to exhaust said cycling control valve andwhen released to connect said cycling control control valve to thereservoir; and throttling means restricting the exhaust of fluid fromthe open end of said large diameter portion.
 18. A fastener driving toolas set forth in claim 17 including check valve bleeding means aroundsaid third piston means providing for fluid flow into the differentialportion of said cylinder for return of said valve element to a normalposition.
 19. A fastener driving tool as set forth in claim 17 includinga delay chamber communicating with said large diameter portion of saidvalve cylinder beyond the stroke of said first piston means.
 20. Apneumatically operated fastener driving tool including a housing havinga cavity defining a fluid reservoir; a cylinder in said housing; apiston slideably mounted in the cylinder; cylinder valve meanscontrolling admission of fluid to and the exhaustion of fluid from oneend of said cylinder in response to the exhaustion of fluid from saidcylinder valve and the admission of fluid from said reservoir to saidcylinder valve, a control valve including a valve body in said housingdefining a valve cylinder of the differential type having a smalldiameter portion and a large diameter portion, said cylinder open atboth ends, a spool-type valve element of the differential diameter typeshiftably positioned in said cylinder for movement between a normal andan operated position having a small diameter part and a large diameterpart, means defining first piston means on said valve element slideablyreceived in said large diameter portion, and means defining second,third and fourth piston means on said valve element slideably receivedin said small diameter portion, first fluid passageway defined betweensaid first and second piston means, second fluid passageway definedbetween said second and third piston means, and third fluid passagewaydefined between said third and fourth piston means; first passage meansopening in said second fluid passage means and communicating with saidcylinder valve means; second passage means opening into said valvecylinder and communicating with said one end of said cylinder, thirdpassage means opening into said small diameter portion of said valvecylinder intermediate the stroke of said third piston and communicatingwith said reservoir, fourth passage means opening into said valvecylinder intermediate the stroke of said fourth piston means; and atrigger valve connected to said control valve through said fourthpassage means effective when depressed to exhaust said control valve andwhen released to connect said control valve to the reservoir.